The present invention is directed to a method and apparatus for measuring the organic carbon content of an aqueous solution.
It has become important that organic carbon measurement devices detect organic contents levels of less than ten parts per billion. The prior art has been limited to detection levels greater than twenty parts per billion TOC.
U.S. Pat. No. 3,958,941 discloses an organic carbon analyzer wherein a deionizing cartridge assembly is used to generate a high purity reference water upon which future measurements are based. Since the resin material in the cartridge assembly is organic in nature, the constant recirculation that occurs in such a device inparts a relatively high organic content to the overall system or background water. The detection limits of such a device is limited by the random changes that occur in the organic content of the system water. It has been found in practice that the background value will vary on an average of plus or minus ten parts per billion Total Organic Content (TOC) at one standard deviation. This indicates that the detection limits of the device is in the range of twenty parts per billion. This renders the device substantially incapable of analyzing the TOC of ultra high purity water process streams used, for example, in a semiconductor industry where TOC is typically below twenty parts per billion.
Other organic measuring devices exist which use a single chamber device, for example the organic analyzer produced by Anatel Model A-100. In this device, a single chamber is used for the oxidation conductivity measurement. Since only a single chamber is used bi-products produced during oxidation can cause a significant error in measurement.
Applicant has developed an improved method and apparatus whereby detection levels of substantially less than ten parts per billion can be measured. Additionally, applicant's invention provides other advantages not taught or suggested in the prior art.